This invention relates to propelling assemblies for engine-driven boats, and more particularly to a propelling system which incorporates steering and propeller submersion control into a single control system.
Propelling assemblies for engine-driven boats have been developed over time in a plurality of forms seeking the best results and manners for the transmission of power from the engine to the pusher propeller itself.
It is not the object of the present invention to describe such a plurality of forms which, for the purpose of example only, could be described as a single shaft extending lengthwise the boat member or as other more intricate and expensive forms consisting of reduction gears, engaging/disengaging means, reverse gears, shaft and propeller, all integrated in a single assembly.
For a clearer understanding of the object of the present invention, it is important that the propelling systems are distinguished by the submersion of the propeller into the water. The usual propelling system suggests a propeller be entirely submerged into the water and sized in a manner to achieve the best possible result, with the propeller itself always kept submerged during operation.
Nevertheless, over the last decades, in the search of higher and higher speeds with greater efficiency, surface propellers have been developed which basically differ from the conventional submerged propellers in their design, which are intended to operate efficiently both submerged or on the water surface, i.e., generating thrust in an efficient manner even when only partially submerged.
The advantage of these propellers, when operated in partial submersion, is the ability to reduce the propeller forward area submerged portion, which, by moving along with the boat, generates a passive power which is much lower than that of the totally submerged propeller.
The significant advantage resulting from such a feature has been absorbed very quickly in the development of the propelling systems by employing surface propellers, although the drawback thereof is low efficiency when the operation is performed in a half-submerged condition under very low speeds. A further drawback is the initial motion of the boat departure.
Conventional system, designed to overcome such difficulties include articulated propelling members wherein the shaft and propeller can be moved and adjusted by two independent systems; one system intended to vertically set the submersion level of the propeller and the other system to use such articulation in the horizontal movement in order to promote the boat steering action.
In this type of assembly, the above described deficiency is resolved by lowering the propelling assembly to a vertical position and thus turning the surface propeller into a submerged propeller on a temporary basis.
If manually operated by a control panel, this process permits the proper adjustment of the submersion level according to the boat speed and makes good use of the propeller efficiency by reducing its displacement-resistant forward area.
Some examples of such propelling systems are objects of U.S. Patents like the one shown in FIG. 1 of U.S. Pat. Nos. 4,544,362 and 4,645,463 and others similarly shown in U.S. Pat. Nos. 2,415,183 and 3,933,116. However, all of these conventional systems present some of the inconveniences described below, or all the inconveniences as in the case of FIG. 1 of U.S. Pat. No. 4,544,363.
Such inconveniences are:
a) The requirement of a pump hydraulic system to perform the manual control of the submersion level. PA1 b) The need of a frequent interference with the hydraulic control to obtain the propeller optimization by adjusting the submersion level. PA1 c) Low reliability of the steering system since the hydraulic system is not protected against external agents, being constantly subjected to the water corrosive actions on the boat external side. PA1 d) Technical-economical infeasibility for the adoption of a mechanical/hydraulic or mechanical system for the steering actuation, since it is constantly submerged into the water. PA1 e) The inoperative condition of the assembly in case of external leakages either in the steering hydraulic system or in the submersion level adjustment hydraulic system. PA1 f) The inoperative condition of the assembly in any case of failure in the submersion level adjustment hydraulic system. PA1 g) Intricate installation due to the assembly of the steering and level control systems which is carried out totally apart from the propelling assembly.